Page 16

SAFETY UPGRADE GUARDS STAINLESS STEEL ROLLING MILL

ABB’s safety PLC has provided the platform for Sandvik Materials Technology to add zoned safety guarding to a large cold rolling mill at its Sandviken plant in Sweden. The mill is a key part of the production line for precision strip steel at the plant.

S

andvik’s cold rolling mill has been upgraded a number of times throughout its life - including recent changes that added servomotors and machine control using ABB’s standard AC500 PLC and touch-screen operator interface panels. The latest upgrade adds safety PLC modules from ABB’s AC500S PLC to the machine control system to enhance the safety of the 20 metre-long mill with a networked architecture using the PROFIsafe protocol over PROFINET to provide independent control of six separate safety zones. The zoned arrangement means that parts of the machine can remain operational while an operator gains safe access to some other zone - where safety is assured by disabling power. Some 50 safety PLC I/O channels are employed to link to gate switch and light curtain guarding and emergency stop buttons. The I/O also monitors pressure switches to sense that hydraulic power is disabled so that maintenance can take place, and controls power supplies to the motor drives. Safe speed control is another aspect of the safety control provided by the new PLC - to ensure that hands or fingers cannot be trapped between the mill’s belt and rollers.

16 This issue is sponsored by — MSA Australia — www.msa.net.au

Sandvik chose ABB’s AC500-S safety PLC for this application because of good experience of the standard non-safety AC500 PLC architecture on both this machine and other machinery control projects. The AC500-S safety PLC also offered Sandvik the possibility of using floating point numbers, which simplified the safety programming required for this project for tasks such as calculating speed. The fact that the standard version of the ABB PLC was already used on the mill measurably simplified the safety upgrade. This is because the safety PLC hardware shares the same look and feel as standard AC500 PLCs allowing safety and non-safety functions to be mixed in the same system. This compatibility includes identical dimensions to CPU and I/O modules, and the same mounting and wiring scheme. The new dual-processor safety CPU module and the safety I/O channels have been integrated alongside the machine's existing AC500 PLC - which controls a total of six DC and AC drives and motors. The DC motors drive the main steel belt and rollers. The AC motors adjust roller position to achieve the desired pressure during strip steel processing. The standard PLC also links with four operator interface panels from ABB’s CP600 series.

Profile for Westwick-Farrow Media

Safety Solutions Jun/Jul 2014  

Launched in April 2003, this bi-monthly magazine provides vital information on safety products and services in the industrial, construction,...

Safety Solutions Jun/Jul 2014  

Launched in April 2003, this bi-monthly magazine provides vital information on safety products and services in the industrial, construction,...